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JUNE,  1875. 


No.  14. 


BULLETIN 


OF    THE 


UNIVERSITY  OF  CALIFORNIA 


SYNOPSIS  OF  A  COUESE  OF  LECTUKES 

ON     THE 

Origin,   Composition,  and  Functions  of  Soils,  and 
their  bearing  on  Agriculture. 

Delivered  at  the  University  of  California,  during  the  first  Term,  1874-5. 
PROF.  EUG.  W.  HILGAKD. 


Definition  of  "  Soil" : 

Different  meaning  as  referred  to  different  plants. 
Judging  of  Soils  by  the  natural  growth. 
Different  forms  of  trees,  etc.,  on  different  soils,  and  er- 
rors resulting  from  their  neglect. 

Exceeding  complication  of  considerations  in  judging  of  the 
value  and  nature  of  soils,  involving  a  very  varied  knowledge 
and  careful  judgment,  or  long  and  costly  experimenting. 

Hence  necessity  for  scientific  examination  on  the  spot,  and 
mechanical  and  chemical  analysis  of  soils;  to  serve  as  guides 
for  practice,  or  practical  tests. 

Necessity  for  cooperation  between  farmers  and  scientists,  to 
prevent  endless  mistakes  and  expense. 
Experimental  Stations. 

s  95 

-73261 


University  Press,  Berkeley 


BULLETIN       OF      THE 


ORIGIN  OF  SOILS. 

Mechanical  and  chemical  disintegration  of  rocks. 

Mineral  composition  of  important  crystaline  rocks. 

Chief  rock-forming  minerals. 

Quartz,  the  Feldspars,  Mica,  Hornblende,  Augite,  Talc 

(Serpentine.) 

Calcareous  Spar  or  Calcite,  Dolomite,  Gypsum,  Apatite. 
Decomposition  of  these  by  atmospheric  agencies;  Water, 

Carbonic  Acid,  Oxygen,  Ammonia. 
Quartz — soluble  and  insoluble  forms. 
Feldspars — formation  of  clays  and  carbonates. 
Hornblende  and  Augite — formation  of  ferruginous  clays, 

loams,  carbonates. 
Mica — difficult  to  decompose. 

Sedimentary  rocks — Sandstones,  shales,  limestones,  how  formed; 
their  composition. 

Character  of  soils  derived  from  these  several  rocks. 

Feldspar  the  source  of  potash. 

Apatite  that  of  phosphates. 
Decomposition  greatly  accelerated  by  pulverization, 

Effects  of  frost  on  rocks, 

Mechanical  Attrition. 

Mechanical  processes  active  in  soil  formation. 
Action  of  flowing  water. 

Action  of  water  charged  with  sand  and  gravel. 
Action  of  glacier  ice. 

COMPOSITION  OF  SOILS. 

General  Soil  Ingredients  are 

Unaltered  Eock-powder. 

Altered  Eock-powder. 

Clay. 

Vegetable  matter. 
According  to  the  proportion  of  these  they  may  be  classed  as 

LIGHT   SOILS  HEAVY   SOILS 


Sandy,       Humous.         Clayey,         Siliceous. 

Definition  of  these  terms. 

Great  diversity  of  sub-classification,  adapted  to  local  circum- 
stances, and  locally  very  important. 
96 


V 


UNIVERSITY       OF       CALIFORNIA. 


DETERMINATION  OF  CHARACTEK  OF  SOILS. 

Observation  in  the  Field — Derivation,  Position,  Depth, 
Substratum,  Natural  growth,  Climate. 

Experience  in  cultivation. 

Taking  of  fair  specimens — difficulty — precautions. 

Examination  of  subsoils  best  adapted  to  general  pur- 
poses. 

PHYSICAL  PROPERTIES  of  soils — quite  as  important   as   chemical 
composition. 

"Lightness" — "Heaviness" — Porosity — Absorption  of 
aqueous  Vapor — Water-holding  power — Capillary  co- 
efficient— Color — Specific"  gravity. 

Difficulty  and  tediousness  of  direct  determination  of  these. 
Mechanical  analysis  as  a  substitute,  sufficient  for  practical  pur- 
poses. 

Elutriation.     Subsidence  method — faults. 

Hydraulic  method. 

Apparatus  of  Noebel — Fresenius — Mueller — Schoene. 

Mixed   character  of  sediments,  and  inconstancy  of  re- 
sults.    Causes — "Flocculation." 
Preliminary  preparation — Boiling — removal  of  gravel  and  clay 

prior  to  washing. 

The    Churn  Elutriator  or  Soil-washer — Construction — Precau- 
tions in  use. 

Character  and  nomenclature  of  sediments. 

Direct  determination  of  Clay  by  precipitation. 

Action  of  common  Salt.     Lime. 

Influence  in  formation  of  bars  at  river  mouths. 
Importance  of  Flocculation — Effects  of  tillage — "Woolly"  condi- 
tion— Tamping  of  clays. 

Molecular  properties  of  sediments — absorptive  coeffi- 
cients— mechanical  resistance. 

Estimation  of  tillability  of  soils;  influence  of  sediments 
on  "  lightness  "  and  "  heaviness  ;"  clay  not  the  only 
factor  of  "heaviness." 

Influence  of  Flocculation. 

Porosity  ^s.  Resistance  to  tillage. 
Absorbing  power  of  Soils. 

Not  in  direct  ratio  to  clay.     Examples. 

Influence  of  Sediments — of  Ferric  Oxide — of  Humus. 
97 


BULLETIN      OF      THE 


"Humus."    Its  origin,  and  influence  on  the  physical   proper- 
ties of  Soils. 
Summary  of  functions  of  physical  soil  ingredients, 

CHEMICAL  COMPOSITION,  AND  ANALYSIS  OF  SOILS. 

Elements  concerned  in  formation  of  Soils. 

"Whence  derived. 

Nutritive  and  inert  Soil  ingredients. 

Ash  ingredients  of  Plants;  derived  from  Soil;  Carbon 
from  Air,  Nitrogen  from  both. 

A  priori  view  of  Soil  analysis — Composition  of  crops. 

Fallacies.  Distinction  between  available  and  unavailable 
portion  of  nutritive  soil  ingredients. 

Difficulties,  and  attempts  to  overcome  them. 

Causes  of  failure — rejection  of  soil  analysis. 

Professor  Johnson's  arguments. 

Discussion    of    objections.      What    soil    analysis    may    fairly 
claim  to  do  for  practice,  in  application  to  virgin  soils. 

To  identify  and  distinguish  soils,  thus  making  past  ex- 
perience available  in  new  regions. 

To  determine  their  prominent  characteristics,  both  phys- 
ical and  chemical. 

To  show  abundance,  scarcity  or  absence  of  important 
soil  ingredients,  thus  indicating  the  general  adapta- 
tion, permanent  value,  and  cheapest  mode  of  im- 
provement, or  maintenance  of  fertility. 

Always  provided,  that  systematic  observation  on  the  spot,  of  all 
circumstances  influencing  cultivation,  and  comparative 
examination' of  soils  of  similar  origin,  be  kept  in  view. 
Mere  columns  of  figures  of  little  use. 
Taking  of  Specimens — details. 

Methods  of  chemical  analysis;  elements  to  be  determined. 

Choice  of  solvents.     General  Analysis — Details. 

Determination  of  Phosphoric  Acid. 

Determination  of  "Humus"  and  Nitrogen. 

FUNCTIONS  OF  THE  SEVEEAL  CHEMICAL  SOIL  INGREDIENTS,  AND  THEIR 

CONDITION  IN  THE  SOIL. 
Outlines  of  Vegetable  Physiology. 

Experiments  on  growth  of  plants  in  soils  devoid  of  or- 
ganic matter;  in  solutions. 

Object  of  the  course   mainly  the  consideration  of  the 
98 


UNIVERSITY       OF       CALIFORNIA. 


indispensable  soil  ingredients,  their  distribution,  func- 
tions and  sources  of  supply. 
Distribution  of  Ash  ingredients  in  Horse  Chestnut,  Beet,  Cereals, 

etc. 

Amount  and  character  of  ashes  in  old  and  young  leaves, 
stems,  wood,  etc. 

Metallic  Elements. 

* 

Potash.     Percentage    contained    in    soils.      Examples.     How 
contained.    Feldspar — Zeolitic  compounds.    Mechan- 
ical absorption.     Liebig's  experiments. 
Laws  of  surface  absorption.    Composition  of  drain  waters. 
Root  crops  especially  exhaustive  of  Potash. 
Potash  manures  in  general. 
Soda.     Inferior  in  importance  to  Potash. 

,  Small  amount  in  soils — easily  washed  out,  yet  rarely  needs 

to  be  supplied. 
Salty  soils — Salt  plants. 
Sodium  salts  used  in  agriculture. 
Oflwr  Alkalies  in  minimum  quantities. 

Lime.       Amount  usually  present  in  soils.       Relation  to   Po- 
tash.    Nutritive  as  well  as  stimulant. 
Largely  present  in  stems. 
General  importance  as  a  soil  ingredient,  both  physical 

and  chemical. 

Effects  on  mechanical  condition  of  Soil. 
"Flocculation." 

Renders  soils  loose,  pervious,  tillable — "warms"  them. 
Chemical  Effects  of  Lime — "fallowing"  action. 

Effects  on  organic  decay,  and  formation  of  "humus." 
How  present — carbonate,  sulphate,  phosphate,  humate. 
Natural  characteristics  of  calcareous  soils — their  growth, 

color,  thriftiness.     Examples. 
Importance  of  a  supply  of  lime  to  Agriculture. 
Magnesia.     Like  lime,  important  stem  ingredient. 

Rarely  deficient  in  soils — seldom  needs  to  be  supplied. 

Partially  replaces  lime. 
Percentage  in  Soils.    Numerical  relation  to  potash.    How 

present  in  soils. 
Copiously  carried  off  in  drain  waters.  Soluble  magnesium 

salts  injurious  to  vegetation. 

Alumina.     Not  a  true  ash  ingredient,  though  often  found  in 
ashes.  99 


6  BULLETIN      OF      THE 

Origin  of  clays.    Varieties.    Kaolin.    Pipe-Clay.    "Soap- 
stone.  "     Brick  Loam. 

Tints  imparted  to  clays  by  Iron — changes  by  oxidation 
and  reduction. 

By  Manganese — by  Carbon — how  recognized. 

Recapitulation  of  the  properties  of  clay  as  a  soil  ingredient. 
Iron.     Widely  diffused,  omnipresent,     Nutritive  as  well  as  me- 
chanically important.     Tonic. 

Hygroscopic  efficacy  of  ferric  oxide;  chemical  inertness. 

Proto  salts  poisonous.     Reduction  of  ferric  oxide  by  veg- 
etable matters.     Yellow  mud  and  blue  mud. 

Bottom  lands — blue  subsoils — "rusting"  soils. 

Iron  in  surface  soils  and  subsoils. 

"White  or  "Crawfishy"  soils — Black  pebble  or  bog  ore  sub- 
soils.    Deterioration  of  soil  thereby:  causes. 

Chalybeate  Springs.     Formation  of  Ferruginous  sand- 
stone. 

Manganese.     Vicarious  of  Iron.     Less  important. 
Copper.     In  very  minute  quantities,  in  wheat,  potashes,  etc. 

Non-metallios. 

Silicon.     Silica  predominant  ingredient  of  soils. 
Sand  and  silicates. 

Apparently  unessential  to  plants  but  very  largely  ab- 
sorbed by  grasses,  pines,  etc.     "Lodging"  of  grain. 
Silica  in  drain  waters — Acid  soils — Action  of  lime. 
Sulphur.     Sulphates  omnipresent.     Small  percentage  in  soils. 
Often  deficient. 

Cheaply  supplied  by  gypsum.     Sulphates  in  drain  water. 
Effects  of  fermentation  on  sulphates.     Iron  pyrites,  etc. 

Remedies. 
Phosphorus.     Phosphates  of  highest  importance  to  nutrition  of 

plants  and  animals. 

Derivation   of  soil  phosphates.     Small  percentage — re- 
lation to  Potash. 
Accumulation  in  seeds.     Small-seeded  plants  on   soils 

poor  in  phosphates. 

Their  deficiency  a  common  cause  of  sterility. 
Must  be  currently  restored  to  cultivated  soils. 
Effect  of  bone-dust  on  old  pastures. 
Chlorine.     Present  in  all  soils  and  plant  ashes. 

100 


UNIVERSITY     OF     CALIFORNIA. 


Correlative  with  Sodium.     Karely  deficient. 
Fluorine.     Very  generally  present  in  small  quantities. 

Most  largely  in  bones. 
Iodine.     Common,  in  traces. 

Carbon.     Ultimately  derived  from  air:    directly  in  part  from 
soil.   Formation  of  humus  by  decay  of  vegetable  matter. 
(Physical  effects  of  humus  on  soils — see  above). 
Chemical  effects  on  soil  ingredients. 

Action  of  Crenic  and  Apocrenic  acids. 

Oxidation  of  humus.     Production  of  carbonic  acid,  the 

universal  solvent. 

Direct  absorption  of  soluble  vegetable  matter. 
Hydrogen.     Absorbed  by  plants  in  shape  of  water. 
Nitrogen.     Highly  important  nutritive  and  constituent  ingredi- 
ent.    Flesh-former. 
Free  nitrogen  of  air  not  assimilable. 
Ammonia  and  nitric  acid  of  atmosphere — absorbed  by 

soil.     Inadequate  for  crops. 
Nitrogen  in  soil.     How  contained?     Small  percentage 

and  largely  unavailable. 
Connection    with    humus — Nitrification    accompanying 

oxidations,  evaporation  etc. 

Ozonization.     Formation  of  Hydrogen  Peroxide. 
Possible  agency  of  microscopic  plants  in  soil. 
Necessity  for  artificial  supply  of  Nitrogen  for  crops.     Ni- 
trogen Theory  versus  "Mineral"  Theory. 
General  effects  of  nitrogenous  manures  on  plants. 

EXHAUSTION  OF  SOILS. 
Eecapitulation : 

'  'All  plant  ingredients  must  be  simultaneously  present  in 
sufficient  quantities.     Absence  of  one  renders  all  inert. " 
"Supplying  that  one  deficient  ingredient  enormously  pro- 
fitable." 

"Excess  of  any  lies  inert  in  the  soil  as  dead  capital." 
Hence  the  necessity  for 

Eolation  of  Crops. 
Causes  of  necessity  for  rotation.     Abstraction  of  different 

ingredients  in  unequal  degrees  by  different  crops. 
Different  depth  of  roots — fibrous  and  tap  roots. 
Examples. 

Eotation  utilizes  soil  resources  best.     Makes  interest  ac- 
101 


BULLETIN      OF      THE 


crue  on  the  whole  soil  capital.     Should  be  the  guidinj 
principle  in  all  cases. 
Order  of  rotation  can  be  determined  by  analysis  of  crops 

MODIFICATION  OF  SOILS  BY  ARTIFICIAL  MEANS. 
By  mechanical  operations. 

Tillage  secures  looseness,  easy  penetration  of  roots,  cii 

culation  of  air,  soil-gases  and  water. 
How  nature  tills — mulching,  frost,  wetting  and  dryii 
Artificial  condition  of  culture;  overriding  of  natural  ac 

aptations  of  soils  and  localities.     Hence  necessity  fo] 

tillage,  preparation  and  cultivation. 
Importance  of  depth  of  soil  for  equalization  of  extreme] 

and  safety  of  crops. 
Depth  of  soil  equivalent  to  cultivating  larger  areas,  bu| 

with  less  labor  and  greater  safety  of  crops. 
In  shallow  soils,  crops  are  at  the  mercy  of  seasons. 
Heavy  soils  need  thorough  tillage  most. 

Deep  tillage — sub-soiling. 
Chemical  and  physical  differences  between  soil  and  sub] 

soil. 
Stirring  versus  turning  up — conditions  under  which  eithej 

may  be  useful  or  injurious. 
Treatment  of  subsoiled  lands,  for  maintenance  of  profit] 

able  productiveness. 
Subsoiling  not  a  preventive  of  exhaustion. 

Drainage —  Under  draining. 
"Believes  wet  soils:"  but  does  a  great  deal  more — us( 

ful  in  all  soils. 
General   plan   of  underdrains.     Various  methods,  tilt 

drains,  log-drains,  brush-drains,  etc. 
Mode  of  action,  difficulties  and  remedies. 
Action  of  underdrains  on  clay  soils.     Analogy  to  subsoil^ 

ing;  protection  against  drouth  by  deepening  of  soil. 
Drained  lands  can  be  tilled  at  all  times;  are  less  cold;  less 

liable  to  surface  washing. 
Advantages  to  public  health. 
By  addition  of  Material — (a.)  "Mechanical  Manures." 

Not  often  profitable  by  themselves — should  be  combined 

with  other  objects. 
Management   of  natural   drainage   to    effect    desirable 


changes. 


192 


Gaylamount       •-.** 
Pamphlet 

Binder 
Gaylord  Bros.,  Inc. 

Stockton,  Calif. 
T.M.Reg.  U.S.  Pat.  Off. 


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